This invention relates to broadly defined sol-gel films for the coating of solid substrates, wherein such sol-gel films provide effective and durable antimicrobial properties. The utilization of such films permits relatively low-temperature production of antimicrobial substrates, such as ceramics, metals (e.g., stainless steel, brass, and the like), plastics (e.g., polyimides, polyamides, polyacrylics, and the like), glass (e.g., borosilicates, and the like), as compared with typical glazes for ceramics and the like. The inventive films comprise, as the primary antimicrobial active ingredients, certain metal-containing inorganic or organic antimicrobial compounds, such as, preferably, metal-containing ion-exchange, oxide, glass, sulfadiazine, and/or zeolite compounds (most preferably, including silver therein as the metal component). Preferably, also, the particular solid substrate to which such films are applied should exhibit substantially high melting and/or heat distortion temperatures to permit high temperature curing of the films to the solid substrate surface (in the range of 100-800xc2x0 C., for example). If the solid substrate melts or distorts, the antimicrobial activity of the ultimate composite is drastically reduced. End uses for such film-coated articles include bathroom fixtures, appliances, kitchen articles and fixtures, furniture, glass, and any other surface that exhibits the high melt and/or heat distortion temperatures noted above and requires antimicrobial characteristics, including certain polymeric films. The specific method of producing such films is also encompassed within this invention.
All U.S. Patents listed below are herein entirely incorporated by reference.
There has been a great deal of attention in recent years given to the hazards of bacterial contamination from potential everyday exposure. Noteworthy examples of such concern include the fatal consequences of food poisoning due to certain strains of Escherichia coli being found within undercooked beef in fast food restaurants; Salmonella contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to Staphylococcus aureus, Klebsiella pneumoniae, yeast, and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various household products and articles. For instance, certain brands of polypropylene cutting boards, liquid soaps, etc., all contain antimicrobial compounds. The most popular antimicrobial for such articles is triclosan. Although the incorporation of such a compound within liquid or certain polymeric media has been relatively simple, other substrates, including the surfaces of textiles and fibers, have proven less accessible. Furthermore, triclosan is a chlorinated compound which may, under certain conditions, release chlorine atoms from the substrate surface. Such ions are potentially hazardous to humans, due to skin irritation upon contact, as well as within environmental effluents, and the like. Additionally, harmful microbes have shown, on occasion, an ability to develop an immunity to the bactericidal properties of triclosan. Also, surface treatments with triclosan have proven ineffective as well since such compounds are easily washed from surfaces when topically applied thereto.
Thus, metal-containing (more specifically and preferably, specific silver-containing) inorganic microbiocides (e.g., ion-exchange, oxide, glass, sulfadiazine, and/or zeolite compounds) have recently been developed and/or utilized as antimicrobial agents on and within a plethora of different substrates and surfaces. In particular, such microbiocides have been adapted for incorporation within plastic compositions and fibers in order to provide household and consumer products which inherently exhibit antimicrobial characteristics. Although such silver-based agents provide excellent, durable, antimicrobial properties, to date no teachings exist which teach or fairly suggest the presence of such inorganic compounds within films or coatings (other than paints or other organically based coatings merely applied and not dried or cured at elevated temperatures thereto) for hard surface substrates, except for limited ceramic coatings as glaze components. These limited attempts at providing hard surface (e.g., ceramic) surface antimicrobial treatments to combat such potentially dangerous bacterial, fungal, etc., problems, have been limited to glazes for ceramic articles, such as within U.S. Pat. No. 5,882,808 to Oku et al. Such a glaze, although providing excellent antimicrobial activity to target ceramic substrates, also exhibits a serious drawback in that the use thereof is limited to ceramic surfaces, and that the temperatures required to cure and thus effectuate the adhesion of such a glaze to the target ceramic is very high (in the range of 1200xc2x0 C.). Thus, in order to practice such an invention, there is a requirement for the generation of and exposure to such very high temperatures. From both safety and cost perspectives, there is thus a need to improve upon such a surface treatment. Furthermore, the development of a lower-temperature method of treating selected surfaces with durable antimicrobial coatings would also permit an expansion in the type of substrates to which such a coating or film may be applied. Basically, nothing has been disclosed or suggested that sol-gel coating films can provide improvements in terms of durable, low-temperature processing, articles, as discussed in greater detail below. Therefore, it remains highly desirable to provide a more versatile surface coating for hard surface substrates, particularly those that are consistently utilized for human hygienic and/or sanitation purposes (such as bathroom and/or kitchen fixtures; e.g., sinks, toilets, showers, and the like) that exhibits effective, and preferably durable, antimicrobial activity. To date, such a coating or film has heretofore been nonexistent within the pertinent prior art and industries.